The present invention is a molding method for a composite consisting of silicone rubber and a thermoplastic resin.
A previously known molding method for composites consisting of silicone rubber and a thermoplastic resin is one in which the thermoplastic resin molding is injection-molded in advance and unvulcanized silicone rubber is put in the cavity of the same mold and pressure molded (monocomponent molding method). Another previously known method is one where the thermoplastic resin is injected and successively unvulcanized silicone rubber is injected into the cavity of the same mold and molded (multicomponent molding method).
However, there have been problems in the monocomponent molding method in that the thermoplastic resin molding tends to deform by heating, is difficult to obtain a high precision composite, and productivity of the method is extremely low. In the multicomponent molding method, which overcomes these problems, a silicone rubber composition, which cures quickly below the softening point of the thermoplastic resin is required. Such a quick curing silicone rubber composition has previously been achieved by adding a large amount of platinum base catalyst or by adjusting the kind or the amount of addition of the hydrosilylation reaction inhibiting compound. Such quick curing silicone rubber compositions are disclosed, for example, in JP (Kokai) 62-207611, and JP (Kokai) 62-264920.
However, the liquid silicone rubber compositions disclosed in JP (Kokai) 62-207611 and JP (Kokai) 62-264920 have a fault in that they have poor storage stability and their curing proceeds in the mixer during molding forming gels. This requires that the mixer section be cooled to below 5.degree. C., which is a cost disadvantage. An addition problem associated with cooling of the mixer section is moisture condensation around the mixer, which can also effect productivity.
The objective of the present invention is to present a method for manufacturing composites of silicone rubber and a thermoplastic resin in high precision and in high productivity.